You don’t have to send your iPhone 4 in right away. After you lock in your price on Nextworth you have 21 days to send in your iPhone. This means that you can lock in your price today, or right before the iPhone 5 is announced and keep it until after the iPhone 5 release date, which we expect on October 13, 14 or 15th.

If you plan on selling your iPhone 4 to pay for an iPhone 5, selling your old iPhone to Nextworth or Gazelle is much easier than selling it on eBay or dealing with Craigslist.

Apple has invited the press to the company’s headquarters on October 4th where the new CEO Tim Cook will take the stage to “talk iPhone.”

We expect that Apple will announce at least one new iPhone, but may announce two devices. If Apple announces two devices, we expect the iPhone 5 with a new look and faster specs, and an iPhone 4S, which will be a cheaper version of the iPhone 4.

If you can’t sell your iPhone 4 right now due to your existing contract with AT&T, you will be able to get new iPhone software shortly after the Apple event. This new software is called iOS 5, and will deliver a host of new features to existing iPhones.